This invention relates to a substrate having at least one fine-wired conductive layer, which is suitable for mounting large-scale integrated (LSI) circuits used in data processing and communication systems.
In a wired substrate mounted with LSI circuits for use in high speed computers implemented with highly dense designing, gold and copper can be used as wiring conductive layers to keep the electric resistances of said conductive layers sufficiently low. Further, polyimide resin having a high insulating capacity and a low dielectric rate can be used as an insulator between the wiring conductive layers of a multi-layered substrate. However, an inadequate adhesion of the polyimide resin insulating layers and the conductive layers consisting of gold or copper, tend to cause their exfoliation from one another with the result that the performance and reliability of the substrate circuit are substantially deteriorated. To obviate these disadvantages, a paper entitled "High Reliability Metallurgical Structure for Multilevel Substrate Wiring" by W. B. Archey et al published in IBM Technical Disclosure Bulletin, Vol. 24, No. 12, May 1982, p. 6370 proposes a wired substrate having a polyimide resin layer in which chrome films are formed over the surfaces of a copper conductive layer as shown in the drawing. However, the chrome films are adversely affected when exposed to an external environment in the process of forming the wiring conductor and the polyimide resin film.